1. Field of the Invention
The present invention relates to an internal combustion engine ignition apparatus mounted in, for example, an automobile, and particularly to an internal combustion engine ignition apparatus in which a current of a primary coil of an ignition coil is interrupted by a switching element, so that a high voltage for ignition is generated in a secondary coil of the ignition coil.
2. Description of the Related Art
In a conventional internal combustion engine ignition apparatus, as a switching circuit for opening and closing a switching element connected to a primary coil of an ignition coil, one having a power supply terminal connected to a battery, an output terminal connected to the primary coil of the ignition coil, an input terminal of an ignition signal voltage, and a reference potential terminal is often used.
In the internal combustion engine ignition apparatus having the four terminals of the power supply terminal, the output terminal, the input terminal and the reference potential terminal, respective control circuits are connected between the power supply terminal and the reference potential terminal, so that the respective circuits can be stably operated while a stable voltage from the battery is applied to the power supply terminal. However, since the four terminals including the power supply terminal is included, the terminal structure becomes complicated.
A conventional internal combustion engine ignition apparatus in which a terminal structure is simplified is disclosed in, for example, Japanese Patent No. 2,749,714. This internal combustion engine ignition apparatus does not have a power supply terminal connected to a battery, but has three terminals of an output terminal connected to a primary coil of an ignition coil, an input terminal of an ignition signal voltage, and a reference potential terminal, and its terminal structure can be simplified. In this internal combustion engine ignition apparatus, a switching element connected between the output terminal and the reference potential terminal is turned on and off by an ignition signal voltage supplied to the input terminal. In addition, a control circuit for controlling this switching element is also connected between the input terminal and the reference potential terminal, and is operated on the basis of the ignition signal voltage.
However, in the internal combustion engine ignition apparatus of this type which has no power supply terminal connected to a battery, since the switching element connected to the primary coil of the ignition coil is driven by the ignition signal voltage supplied to the input terminal, there is a disadvantage that variation in the level of the ignition signal voltage degrades the ignition characteristic. For example, in an on state of the switching element, although a current increasing with the lapse of time flows through the primary coil of the ignition coil by the influence of its inductance, when the level of the ignition signal voltage is low in the on state of the switching element, energization to the primary coil of the ignition coil is performed in the state where the on resistance of the switching element is relatively large, so that the switching element is turned off in the state where the current of the primary coil of the ignition coil is not increased to a sufficient value, and there occurs a case where a sufficient ignition voltage can not be generated, ignition energy to the engine is insufficient, and engine output is lowered or misfire occurs in which ignition for the engine is not performed.
Besides, in the on state of the switching element, when the ignition signal voltage pulsates by noise, the flowing current of the primary coil of the ignition coil is also varied, and there is a fear that erroneous ignition occurs at an erroneous timing which is not the ignition timing, and by the pulsation of the ignition signal voltage, even if the erroneous ignition does not occur, the switching element is turned off in the state where the current of the primary coil of the ignition coil is not increased up to a sufficient value, so that a sufficient ignition voltage is not generated, the ignition energy for the engine is insufficient, and the engine output is lowered.